I've seen this happen to a couple of post where they will be flagged as a duplicate post or an inferior post, even though they are different. I can't get the post ID since they have been deleted, and I didn't think it would happen again so I didn't bother to remember it the second time.
The first of the two that I've notice this happen to was a post that combined post #2306460 and post #2306464 into a single image. Idk why that would be considered inferior to either of the two used to create it.
The second post was a WEBM version of post #2198571. The WEBM was flagged as inferior and deleted, even though it was WEBM and the parent was not.
To my understanding, both of these were unjustified deletions of perfectly valid posts. This is probably happening more than what I've been able to notice. It's kind of annoying.
I think some kind of way for users to challenge a flag might make whoever is reviewing it to do a double take before they decide to delete the post.